Semester 2 - GI infections

Question 0

How does peristalsis act as a barrier to infection?

Answer 0

Inhibits adherence, colonization of pathogenic microorganisms, constant flushing action

Question 1

What are the physical barriers to infection in the GI tract?

Answer 1

Peristalsis and flow of liquids through the GI tract.
pH
Mucus
(Epithelial cell turnover in GIT?)

Question 2

How does pH act as a barrier to infection?

Answer 2

Inhibits the growth of pathogenic microorganisms

Determines microbial blor in various areas of the GIT

Question 3

How does mucus act as a barrier to infection?

Answer 3

Aids in flushing action
Provides a barrier to susceptible cells
Contains immune cells, antimicrobial peptides etc

Question 4

What are some innate immune defenses found in the mucosa?

Answer 4

GALT
Peyer’s patches in SI
M cells (sample and deliver antigens to basolateral APCs)
Defensins (b-defensin, lysozyme, anti-microbial peptides AMPs etc)

Question 5

How does GI flora contribute as a barrier to infection?

Answer 5

Inhibits the growth of pathogenic bacteria
Support the growth of other beneficial bacteria
Aid in digestion

Question 6

What are the factors influencing susceptibility to GI infection?

Answer 6

Anatomical/mechanical: any obstruction to flow
Acidity: Changes to pH affect growth of flora, pathogens
GI flora: change in growth/composition of normal flora, pH, antibiotic use, diet etc
Immune composition: peyer’s patches inflammation

Question 7

What are some sources of GI infection?

Answer 7

Fecal-oral transmission - stability of pathogens (food, water, person-to-person)
Hematogenous spread from a primary site (rare)
Bacterial, viral, parasitic

Question 8

What is gastroenteritis?

Answer 8

Inflammation in bowel movement, increased looseness of stool

Dehydration, electrolyte loss

Question 9

What is diarrhea?

Answer 9

Increase in bowel movements, increased looseness of stool

Dehydration, electrolyte loss

Question 10

What is dysentery?

Answer 10

Infection and inflammation of the large intestine. Associated with blood and pus in feces, abdominal pain and cramping

Question 11

What is enterocolitis

Answer 11

Inflammation of the small and large intestine

Abdominal bloating, bloody stool, constant urge to have a bowel movement

Question 12

What is enteric fever (typhoid/paratyphoid)?

Answer 12

Fever, headache, malaise, anorexia
Hepatosplenomegaly, transient rash on trunk
May lead to intestinal perforation, hemorhage

Question 13

What is a food borne illness?

Answer 13

Any illness acquired from food

Includes food infection, food poisoning

Question 14

What is food infection/food-associated infection?

Answer 14

Pathogen colonizes/multiplies within the GIT

I.e. E.coli, salmonella

Question 15

What is food poisoning/food intoxication?

Answer 15

Associated with toxin production by pathogen
Does not always require the presence of viable pathogen (i.e. improperly cooked/stored food)
i.e. C. botulinum, S. aureus

Question 16

What do bacterial GI infections cause and are typically acquired?

Answer 16

Typically acquired from food and cause both food infection and food intoxication (many associated with an enterotoxin)

Question 17

What is the pattern of a bacterial infection?

Answer 17

Fluid and electrolyte secretion may be a function of enterotoxin
Invasive pathogens may cause damage to intestinal epithelium (bleeding, perforation, ruffling of epithelial cells in the GIT)
Activation of TLRs (associated chronic inflammation eg Crohn’s), NLRs leads to intestinal inflammation

Question 18

What is the pattern of a viral infection?

Answer 18

Generally cause food infection (some viruses produce potent viral enterotoxins)
May be acquired from food or infected individuals (highly transmissible)
Activation of multiple pattern recognition receptors associated with intestinal inflammation

Question 19

What is the pattern of a parasitic infection?

Answer 19

Generally cause food infection
Most have limited distribution: associated poor hygiene/water sanitation etc
May be acquired from food/water
Activation of complement, eosinophils (inflammation)
Internalization of host cells in the intestinal lining may lead to damage, blood sucking from the intestine may lead to nutrient deficiency and anemia
Parasitic infections generally associated with Th2 adaptive immune response

Question 20

What are the clinical symptoms of a GI infection?

Answer 20

Most mild GI infections require only management of symptoms
Fluid and electrolyte replacement
Nutritional replacement
Probiotics

Question 21

What type of infection is a stool sample valuable for?

Answer 21

Generally for parasitic infection (macroscopic, microscopic)

Stool cultures may be used for prolonged/severe bacterial infections

Question 22

What are some quantitative methods for the diagnosis of GI infections?

Answer 22

Serological analysis (PCR, ELISA)
Not super accessible?

Question 23

What is the treatment of GI infections?

Answer 23

Antibiotics not generally recommended (restoration flora important)
Macrolide abx for severe bacterial infection
Metronidazole broad spectrum abx/antiparasitic
Anti-emetic anti-mortality drugs, electrolyte and fluid replacement as necessary

Question 24

What vaccinations to GI infections are there?

Answer 24

Rotavirus
Cholera
Traveller's diarrhea (ETEC)
Hep A
Barriers to immunization??

Question 25

DDx considerations

Answer 25

For similar infections consider
Age
Immune status
Source of transmission - food water nosocomial
Prevalence of candidate infections in a given location
Extra-intestinal symptoms
Incubation period and length of symptoms

Question 26

When are precise diagnoses for infectious disease of the GIT crucial?

Answer 26

?